Wierd acceleration stumble
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Senior User
Joined: Jun 2010
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Wierd acceleration stumble
This problem has perplexed since day one with this truck:
If I have a heavy load +7k pounds, or stomp on it from a stop light here is what happens:
Pulls great to 1500 rpm, boost kicks in, slams into second
Pulls great to like 2200, then rpm drop by 300-500 rpm, then back to pulling hard, up shifts, holds 3rd well, yada yada,
Any ideas on the rpm drop. Probably not related but here are things I have done to the truck:
Genuine TYMAR intake,
3" DP
New OE fuel pump
Ford replaced CPS on the recall
As always, thanks for the help
If I have a heavy load +7k pounds, or stomp on it from a stop light here is what happens:
Pulls great to 1500 rpm, boost kicks in, slams into second
Pulls great to like 2200, then rpm drop by 300-500 rpm, then back to pulling hard, up shifts, holds 3rd well, yada yada,
Any ideas on the rpm drop. Probably not related but here are things I have done to the truck:
Genuine TYMAR intake,
3" DP
New OE fuel pump
Ford replaced CPS on the recall
As always, thanks for the help
Thread Starter
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Senior User
Joined: Jun 2010
Posts: 141
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I thought fuel filter and FPR screen as well. Put the pump in less than 500 miles ago, and while there I re oringed the fuel bowl, totally cleand the screen, and put in a new filter.
Now, TPS, I didn't think of that. But wouldn't it stumble every time at that "exact spot"? So like in 1st, 2nd, 3rd, OD etc?
Now, TPS, I didn't think of that. But wouldn't it stumble every time at that "exact spot"? So like in 1st, 2nd, 3rd, OD etc?
Last edited by FLATTIE; Jun 9, 2011 at 09:31 PM. Reason: because I can't spell
Fleet Mechanic
Joined: Aug 2007
Posts: 1,508
Likes: 2
From: The boonies by Dallas OR
There is nothing wrong with your truck. That is the torque converter clutch locking up. When the converter is free it will slip 300 to 500 RPM and when it locks the engine slows down to the speed of the transmission input.
The lock clutch only engages in first or second gear if you're over 3/4 throttle for 10 seconds. It does this to limit heat build up under high load. Running unloaded it won't be in first or second for 10 seconds if you stomp it so unless you tow you'll never know that the truck does this. I can tell you that if you pull over 12,000 lbs you can get it to do it in first gear too.
You can put this to use if you ever have a long steep hill to climb. Put the truck in second and then stay on it until you lock the torque converter. It will stay locked until you let off the throttle. It will stay locked even if you slack off on the throttle to go around corners.
The lock clutch only engages in first or second gear if you're over 3/4 throttle for 10 seconds. It does this to limit heat build up under high load. Running unloaded it won't be in first or second for 10 seconds if you stomp it so unless you tow you'll never know that the truck does this. I can tell you that if you pull over 12,000 lbs you can get it to do it in first gear too.
You can put this to use if you ever have a long steep hill to climb. Put the truck in second and then stay on it until you lock the torque converter. It will stay locked until you let off the throttle. It will stay locked even if you slack off on the throttle to go around corners.
Thread Starter
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Senior User
Joined: Jun 2010
Posts: 141
Likes: 0
There is nothing wrong with your truck. That is the torque converter clutch locking up. When the converter is free it will slip 300 to 500 RPM and when it locks the engine slows down to the speed of the transmission input.
The lock clutch only engages in first or second gear if you're over 3/4 throttle for 10 seconds. It does this to limit heat build up under high load. Running unloaded it won't be in first or second for 10 seconds if you stomp it so unless you tow you'll never know that the truck does this. I can tell you that if you pull over 12,000 lbs you can get it to do it in first gear too.
You can put this to use if you ever have a long steep hill to climb. Put the truck in second and then stay on it until you lock the torque converter. It will stay locked until you let off the throttle. It will stay locked even if you slack off on the throttle to go around corners.
The lock clutch only engages in first or second gear if you're over 3/4 throttle for 10 seconds. It does this to limit heat build up under high load. Running unloaded it won't be in first or second for 10 seconds if you stomp it so unless you tow you'll never know that the truck does this. I can tell you that if you pull over 12,000 lbs you can get it to do it in first gear too.
You can put this to use if you ever have a long steep hill to climb. Put the truck in second and then stay on it until you lock the torque converter. It will stay locked until you let off the throttle. It will stay locked even if you slack off on the throttle to go around corners.
Thanks
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